1. Field of the Invention
The present invention relates to a sewing machine needle having less possibility of causing stitch skipping or fabric yarn breakage, irrespective of high-speed and multifunction sewing machines and diversified materials being used.
2. Description of the Related Art
Sewing machines used in sewing are roughly classified into ones for industrial use and ones for domestic use.
The industrial sewing machines are generally used at high rotational speeds from the viewpoint of pursuing productivity, and the rotational speed thereof may come up to as high as 8000 rpm. In automated industrial sewing machines, seams are formed in multi-directions and loops that are important for formation of the seams tend to become unstable under the influence of sewing threads having a certain twist angle.
A fabric feeding mechanism of automated sewing machines such as pattern seamers or cycle sewing machines employs an X-Y table to realize multi-directional sewing. When a tip of a rotary hook passes a scarf of a sewing machine needle, minute oscillations of the X-Y table cause a large shaking of the needle from the scarf thereof to a needle point thereof. As a result, the tip of the rotary hook fails to catch a loop so that stitch skipping is liable to occur.
In the conventional techniques, for the purpose of suppressing such stitch skipping arising from the shaking of the needle, the dimensions of a needle dropping portion or needle dropping hole of the rotary hook are lessened with respect to the thickness of the sewing machine needle so that the clearance therebetween is minimized to reduce the shaking of the needle. Due to a tip end portion of the sewing machine needle having to reciprocate through the needle dropping hole, however, the dimensions of the needle dropping hole can not be made smaller than the thickness of the needle in a direction in which a needle eye extends. In addition, since the tip end portion of the conventional sewing machine needle is tapered, the clearance between the needle and the needle dropping hole inevitably becomes large.
On the contrary, the household sewing machines have seldom experienced such problems so far unlike the industrial sewing machines since the former is basically used at a low rotational speed. Recently, however, more and more household sewing machines have come to employ an additional embroidery function. Since their mechanisms are similar to those of the automated industrial sewing machines, the household sewing machines are also facing the same problems as those of the industrial sewing machines.
A variety of materials used for sewn products have diversely been developed. Recent tendency is toward frequent development of materials rich in stretchability, which have come to be used for sewn products called heavy products such as jeans, which use has not hitherto been present by any means. Extremely delicate jersey-based materials have also come to be used for automobile seats and have posed another essential problem of fabric yarn breakage in addition to the sewing problems such as stitch skipping and needle breakage.
Thus, recent years have not required addressing only a single sewing trouble as before but have required a high-performance sewing machine needle capable of effectively coping with a plurality of sewing troubles, especially, combined troubles of stitch skipping and fabric yarn breakage.